This invention relates to centrifugal clutches and more particularly relates to novel and improved centrifugal clutches having high density cam members which are urged outwardly under centrifugal force in order to activate the clutching elements.
Centrifugal clutches have been developed for motorcycles utilizing one or two rows of balls or other cam members which would move outwardly in response to rotation of a drive shaft to cause the clutch plates to move into engagement with one another. However, in certain applications it was found that there is insufficient centrifugal force generated to clamp the clutch plates together without substantial slipping or without utilizing a larger size case or cover which exceeds the space allowances within stock engine cases. For example, space is at a particular premium in motorcycle clutches incorporating a manual override mechanism, such as, that set forth and described in copending application for U.S. patent Ser. No. 09/877,518 for AUTOMATIC CLUTCH WITH MANUAL OVERRIDE CONTROL MECHANISM.
Accordingly, there is a need for a cam mechanism for centrifugal clutches which can generate the necessary force to clamp the clutch plates together without substantial slipping or increase in the size of the clutch case or cover. At the same time it is desirable to provide a cam-actuating mechanism which requires a minimum of manual pressure to engage or disengage the clutch elements with a manual override mechanism while at the same time being highly sensitive to acceleration in speed to effect engagement of the clutch elements. Still further, a controlled amount of slippage may be built into the hub drive for the clutch in order to prevent damage to the drive train resulting from the application of shock loads.
It has been the practice in motorcycle clutch casings or housings to utilize a generally basket-like housing having circumferentially spaced side walls and to secure the cover by threaded fasteners to the free ends of the side walls and which tends to weaken the connection at the connecting or fastening points between the cover and ends of the side walls, and requires that the cover be mounted on or externally of the housing side walls. Accordingly, there is a need for an improved method of attachment between the cover and side walls but which will distribute the connecting points over a wide area between the cover and side walls, avoid time-consuming attachment of individual fasteners and enable mounting of the cover flush or inset with respect to the housing side walls so as to result in a more compact assembly.